11111...31111 (55-digits)

This number is a prime.

                11111 1111113333 3331135555 3113575311 3553113531 1331131111

+

1 1 1 1 1 1 1 1 1 1
1 3 3 3 3 3 3 3 1
1 3 5 5 5 5 3 1
1 3 5 7 5 3 1
1 3 5 5 3 1
1 3 5 3 1
1 3 3 1
1 3 1
1 1
1

A triangle-congruent prime consisting of only odd digits. [Patterson]

Printed from the PrimePages <primes.utm.edu> © G. L. Honaker and Chris K. Caldwell